Needle steering by shaft manipulation

ABSTRACT

A method and apparatus for steering of a flexible needle into tissue using a steering robotic platform for manipulation of the needle shaft, and by use of a semi-active arm for locating and orienting of the steering robot on the patient&#39;s body. As opposed to other steering methods, the robot does not hold the base of the needle, which is its proximal region, but rather grips the shaft of the needle by means of a manipulatable needle gripping device, near its distal end. The needle gripper attached to the robotic platform may be equipped with a traction assembly to provide motion to the needle in its longitudinal direction, such that it co-ordinates the entry of the needle with the desired entry angle. The gripping of the needle at its distal end, close to its insertion point, provides the needle manipulator with a low profile, with concomitant advantages.

FIELD OF THE INVENTION

The present invention relates to the field of devices for needlesteering and their use in image-guided robotic needle steering.

BACKGROUND OF THE INVENTION

Many routine treatments employed in modern clinical practice involvepercutaneous insertion of needles and catheters for biopsy and drugdelivery and other therapies. The aim of a needle insertion procedure isto place the tip of an appropriate needle safely and accurately in atarget region, which could be a lesion, organ or vessel. Examples oftreatments requiring needle insertions include vaccinations, blood/fluidsampling, regional anesthesia, tissue biopsy, catheter insertion,cryogenic ablation, electrolytic ablation, brachytherapy, neurosurgery,deep brain stimulation and various minimally invasive surgeries.

Guidance and steering of needles in soft tissue is a complicated taskthat requires good 3-D coordination, knowledge of the patient anatomyand a high level of experience. Therefore robotic systems have beenproposed for performing these functions. Among such robotic systems arethose described in U.S. Pat. No. 7,008,373 to D. Stoianovici, for“System and method for robot targeting under fluoroscopy”; and in U.S.Pat. No. 5,572,999 to Funda et al, for “Robotic system for positioning asurgical instrument relative to a patient's body”; and in the productdata sheets on the Innomotion robot, as provided by Innomedic GmbH, ofPhilippsburg-Rheinsheim, Germany.

All of these systems are guiding systems that help in choosing theinsertion point and in aligning the needle with the target. Theinsertion is then done by the surgeon who pushes the needle along thestraight line. Such systems usually work with 3-D data taken before theprocedure, typically by CT or MRI. The 3-D reconstruction of the patientanatomy is done first. Then the needle is registered to the 3-D anatomyand the robot can orient a cannula so that it will be aligned with thetarget. Through that cannula the doctor inserts a needle assuming thatthe needle will not deviate from a straight line and that it will hitthe target. A problem with this method is that both needles and tissueare flexible, and the needle therefore does not always proceed in astraight line even in soft tissue. It may deviate from the plannedstraight path, and methods are needed for ensuring that it does reachthe intended target region.

A method for needle steering which is based on the lateral forcesexerted on the tip of flexible beveled needle has been described inpublished US Patent Application US 2007/0016067 A1 to R. J. Webster IIIet al, for “Distal Bevel Tip Needle Control Device and Algorithm”. Thisapplication describes a needle driver which grasps the base of thebeveled needle and drives the needle shaft by pushing it forlongitudinal entry, and rotating it for steering.

In PCT publication No. WO 2007/141784 to D. Glozman et al, for“Controlled Steering of a Flexible Needle”, there is described anothermethod in which the base of the needle is held by a robot, and theneedle is steered by manipulation of the needle base by the robot.

However, all of the methods and systems described above use needlesgripped robotically or otherwise, at their proximal ends, remote fromthe insertion point into the patient. This results in the need for alarge workspace, which may be especially problematic in the realm ofimaging systems, where headroom above the supine patient is oftenlimited. There therefore exists a need for a more compact method ofmanipulating a needle during the insertion process into a subject.

The disclosures of each of the publications mentioned in this sectionand in other sections of the specification, are hereby incorporated byreference, each in its entirety.

SUMMARY OF THE INVENTION

The present disclosure describes a method and apparatus for steering ofa flexible needle inside soft tissue by manipulation of the needleshaft, and by use of a semi-active device for locating and orienting ofthe steering robot on the patient's body. As opposed to other steeringmethods, the robot does not hold the base of the needle, or a proximalpoint close to the base of the needle, but rather grips the shaft of theneedle by its distal part, closer to the insertion point into thepatient, by means of a manipulatable needle gripper. The combination ofthe needle gripper and the robotic platform for manipulating the needlegripper is called in this application, a robotic needle manipulator.

The robotic needle manipulator should be able to move with at least 4degrees of freedom. The minimal four degrees of freedom enableorientation and positioning of the robotic needle manipulator. Twodegrees of freedom are needed for positioning the entry point of theneedle and two for orientation. Motion perpendicular to the plane is notessential, since the insertion motion of the needle may be provided by apushing motion generated within the robotic needle manipulator, asdescribed below. Since the robotic needle manipulator does not have togenerate the motion required for insertion of the full length of theneedle, which could be considerable, the workspace required by thesystem is significantly smaller than that of prior art systems which doperform the robotic insertion themselves. However, use of a roboticplatform with more than 4 degrees of freedom may also be advantageous,though the use of the direction of freedom in the direction parallel tothe needle will not generally be used for inserting the needle, becausethe large travel generally required for inserting the needle mayconflict with the need to maintain a low profile workspace of therobotic needle manipulator.

Besides the needle orientation and positioning functions generated bythe robotic actuator, as described above, the robotic needle manipulatorshould also be able to insert the needle by means of a mechanism whichmoves the needle in its longitudinal direction. This mechanism can beeither a mechanical system designed to grip the needle shaft and to moveit inwards and outwards, or alternatively, the “mechanism” could simplybe a manual operation by the medical personnel inserting the needle byhand while the gripping action of the robotic needle manipulator isreleased, or alternatively, not even fitted, with the needle held freelyin a cannula.

In addition, rotation of the needle may be useful for use with beveledneedle guidance systems, or, simply in order to keep the bevel at 90degrees to the imaging plane so that if lateral forces develop duringthe insertion, the deviation generated because of the beveled needlewill be in the imaging plane, where imaging is optimal for detection ofsuch a deviation. The proposed system can work with various medicalimage modes, such as CT, MRI, PET or Ultrasound.

The needle may be inserted either continuously or step by step,requiring operator approval for each step. A major innovative aspect ofthis system is in the manipulation of the needle by means of its distalportion.

One advantage of the systems described in this application is that theworkspace required for the robot is significantly smaller than for priorart systems, where the robot manipulates the base of the needle, which,for a long needle, can be 10 cm. or even more from the entry point atthe tip of the needle. The workspace can be as little as the order of 10millimeters as opposed to several centimeters for the prior art systems.In the systems described in this application, the longitudinal needlemotion is mechanically separated from the lateral manipulations of theneedle. A characteristic of these implementations of the devices of thisdisclosure is that the needle driving mechanism is capable of drivingneedles of variable lengths while the dimensions and workspace of thedriving mechanism does not depend on the length of the needles. In priorart systems, the longitudinal needle insertion is either not availablerobotically, or if available, it requires the manipulator to have arange of motion at least as long as the length of insertion of theneedle.

Examples of needle base driving and needle shaft driving will be shownbelow by a numerical simulation. A smaller workspace allows the use of asmaller robot which is advantageous in such medical applications. Such aworkspace of only 10 millimeters or so is advantageous from a safetypoint of view. The robot is then incapable of accidentally movingsignificantly and of injuring neighboring organs.

Because of their low profile, the robotic needle manipulators describedin this application can be easily placed on the patient's body, which isalso advantageous because this compensates for patient motion during theprocedure—the robot moves with the patient. The robot can be placed onthe patient directly and be connected with belts, or adhesives, therebyaffixing its lateral position on the patient's skin.

Furthermore, the low profile enables the robotic needle manipulator tobe used more readily in the limited space of a CT or otherthree-dimensional imaging system.

According to an exemplary aspect of the present invention, the roboticneedle manipulator is supported by a semi-active support arm whosepurposes may be one or more of the following:

(i) to append the robotic needle manipulator to the patient's bodysurface by applying a gentle force, and(ii) to track the robot position in real-time.

The semi-active arm may have 3 or more degrees of freedom, andpreferably 6, in order to be able to laterally locate the robot abovethe needle entry point and to orient the robot plane relative to thepatient's body. The semi-active arm may comprise a series of linksconnected by joints, as in a serial robot. However, it is to beunderstood that a parallel robot or a hybrid serial-parallel robot mayalso be used in this application. For a serial robot, each suchsemi-active joint should have an encoder which monitors the rotation ofthe joint, so that the position and orientation of the end effector canbe calculated by solution of the forward kinematics problem. Thesemi-active arm can, on the other hand, alternatively be fully passive,meaning that there are no motors in the joints and the joints can berotated freely unlocked, or there may be motors or springs operating onone or more joints so that the angle of at least one joint can becontrolled. Alternatively, one or more joints can be locked and otherspassive. Regardless of the actual configuration used, the encoders onthe joints, if fitted, can be used as the sensors for determining theposition of the semi-active arm relative to the patient's body, hencedetermining the position and orientation of the robot, such as for thepurposes of the registration described herewithin.

Control of one or more joints is useful for solution of the respirationgait problem (respiration compensation), where the robot should movesynchronously with movements of the patient's body. An additionalfunction of the semi-active arm may be to monitor the respiration of thepatient. The semi-active arm reduces the need for placing externalsensors on the patient's skin, as is done in prior art methods, in orderto monitor the stages of the breath cycle of the patient. Since therobotic needle manipulator maintains contact with the patient's chest,its sensors are able to define the breath cycle of the patient.

A particularly useful configuration of the support arm is to provide itwith positive control in the direction perpendicular to the patient'sbody surface, such as by use of a spring, such that it exerts sufficientpressure that the robotic needle manipulator remains in contact with thepatient's skin, yet allows the robotic needle manipulator to rise andfall with the patient's breathing cycle. At the same time, the otherdirections of freedom of the robotic needle manipulator control systemmay advantageously be maintained sufficiently stiffly controlled thatthe robotic needle manipulator remains nominally constrained by thesupport arm to its predetermined position on the subject's body at theneedle insertion point, yet allows some level of freedom of movementshould the patient move laterally during the procedure due to coughingor discomfort or the like.

Additionally, the need for sensors on the semi-active arm may bedictated by the need to maintain registration of the robot position withthe CT coordinate system. The initial robotic registration to establishcorrect co-ordinate transformation between the robot and CT systems,becomes invalidated by the patient's breathing motion, which also movesthe robot. The sensors in the semi-active arm are able to track therobot position, in order to maintain the correct current co-ordinatetransformation from the initial registration procedure, even as therobot moves.

An additional advantage of connecting the robot via a semi-active arm isthat the arm with the robot and the patient now move together and it ispossible to perform volume scans of the patient with the needleinserted. In order to perform a volume scan, the CT bed needs to move.When the needle is inside the patient and the CT bed moves, the needleand the robot move with the bed and the patient, so there is no relativemovement between the needle and the patient.

There is thus provided in accordance with an exemplary implementation ofthe devices described in this disclosure, a system for needle insertioninto a subject, comprising:

(i) a robotic platform having a plurality of degrees of freedomproviding the needle with a desired pose, and(ii) a needle gripper attached to the robotic platform, the needlegripper being activated to provide motion to the needle in itslongitudinal direction,wherein the needle gripper grips the shaft of the needle distally to thebase of the needle.

Such a system may further comprise a positioning system for positioningthe robotic platform close to the point of insertion of the needle intothe subject. Furthermore, the needle gripper may comprise at least apair of rollers on either side of the needle, such that co-ordinatedrotation of the rollers causes the needle to move in its longitudinaldirection. Additionally, a needle rotation mechanism may beincorporated, such that the needle can be rotated about its axis. In yetother implementations, the needle gripper may be adapted to release itsgrip on the needle, such that the needle can move longitudinally freely.

In yet other implementations of the needle insertion systems of thepresent application, the robotic platform may comprise a base plate,such that the robotic platform can be positioned with the base plate injuxtaposition to the skin of the subject. Furthermore, the pose may beadjusted in co-ordination with activation of the needle gripper suchthat the orientation of the needle can be adjusted as the needle isinserted into the subject.

Furthermore, in any of the above-described systems, gripping of theneedle shaft distally to the needle base is such that the system canoperate without any part thereof extending further from the subject thanthe base of the needle. In some exemplary implementations, the workspaceof the system may not extend more than 50 mm from the point of insertionof the needle, and in other implementations not more than 30 mm. and inyet other implementations, not more than 20 mm.

In any of the above-described systems, the robotic platform may be aparallel, a serial or a hybrid robotic platform.

There is further provided in accordance with another exemplaryimplementation of the devices described in this disclosure, a system forneedle insertion into a subject, comprising:

(i) a robotic platform for aligning and inserting the needle into thesubject,(ii) a support arm for aligning the robotic platform close to the pointof insertion of the needle into the subject, and(iii) a sensor system for detecting motion of the body of the subjectclose to the point of insertion of the needle,wherein the sensor system provides commands for the robotic platform,for insertion of the needle in co-ordination with the detected motion ofthe body of the subject.

The motion of the body of the subject mentioned hereinabove in relationto such a system, may be breathing related motion. Additionally, thesupport arm may be designed to apply pressure on the robotic platform,such that the robotic platform remains in contact with the subject'sbody, and the support arm may be such that its motion is essentiallyunconstrained in a direction perpendicular to the surface of thepatient's body, such that the robotic platform moves freely with motionof the subject's body. Furthermore, the motion of the support arm may bepartially constrained in directions parallel to the surface of thepatient's body, such that the robotic platform is generally constrainedby the support arm to a predetermined position on the subject's body.

Yet other implementations perform a method for insertion a needle into asubject, comprising:

(i) providing a robotic platform having a plurality of degrees offreedom to align the needle at its desired pose,(ii) providing a needle gripper for attachment to the robotic platform,(iii) using the needle gripper to grip the shaft of the needle distallyfrom the base of the needle, and(iv) activating the needle gripper to provide motion to the needle inits longitudinal direction.

An additional exemplary method for inserting a needle into a subject,may comprise:

(i) providing a robotic platform for aligning the needle for insertioninto the subject,(ii) providing a support arm for aligning the robotic platform close tothe point of insertion of the needle into the subject,(iii) detecting motion of the body of the subject close to the point ofinsertion of the needle, and(iv) using the detected motion of the body to provide commands for therobotic platform, such that the needle can be inserted in co-ordinationwith the detected motion of the body of the subject.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 shows overall view of a system of the present disclosure, used tomanipulate a needle under the guidance of a CT imaging system;

FIG. 2 is a schematic view of the robotic needle manipulator attached tothe patient base plate for insertion into an imaging system;

FIG. 3 is a schematic view of a complete robotic needle manipulatorshown holding a needle remotely from the needle base;

FIG. 4 is another schematic view of the robotic needle manipulator ofFIG. 3;

FIGS. 5 and 6 show schematically a complete robotic needle manipulatorat two different insertion angles, incorporating a needle drivingmechanism employing rotation of two or more rollers, such that theneedle insertion can be performed under robotic control;

FIG. 7 is a graphical representation of a prior art example of needlesteering by steering of the needle base; and

FIG. 8 is a graphical representation of an example of needle steeringusing the distal shaft gripping method of the present disclosure,showing the space saving advantages over the prior art method shown inFIG. 7.

DETAILED DESCRIPTION

Reference is first made to FIGS. 1 and 2 which show the overall view ofa system used to manipulate the needle under the guidance of an imagingsystem, such as CT or MRI guidance. However, it is to be understood thatthe needle steering manipulation technique and the needle manipulatingrobot is not limited to use with CT or MRI imaging modality, but can beused with any existing imaging modality such as Ultrasound, PET, or thelike.

FIG. 1 shows an exemplary system mounted on a CT system. The system doesnot need to be connected to the CT system directly. The robotic needlemanipulator 11 may be connected to the base element plate 12 via asemi-active arm 13, which may be connected to the base element via anarched support arm 21. The base element may be placed on the imagingsystem bed 14 and moves together with the imaging system bed.Alternatively, the support arch could be mounted directly on the imagingsystem bed.

Reference is now made to FIG. 2 where the complete system is shownwithout the CT. The miniature robot 11 is shown connected to the baseelement 12 via a semi-active arm 13. The semi-active arm is so-calledbecause it has one or more actuators, but does not generally need asmany actuators as its number of degrees of freedom, such that not all ofthe joints need to be controlled. That would make the arm unnecessarilycomplex and costly for its function, which is only to position therobotic needle manipulator in the correct position relative to theneedle entry point and the patient's body pose. The base element,preferably having the shape of the CT-bed, should be stiff enough sothat the patient can lie on it and firm enough that the connection ofthe arched support arm 21 to it will be rigid enough.

In the example shown, the semi-active arm has 5 degrees of freedom, 3for positioning of the base of the robotic needle manipulator anywhereon the patient's body, and 2 for orienting of the robotic needlemanipulator to be generally parallel to the patient's body, andadvantageously in contact with the subject's skin.

Reference is now made to FIG. 3 where a complete robotic needlemanipulator is shown. A robot 11 is shown holding the needle 31. Forpurposes of illustration, the robot is based on the well-knownStewart-Gough platform, which was introduced in 1965, though it is to beunderstood that this is just an exemplary implementation, and any othersuitable type of robot could be used. The robot has 6 degrees-of-freedomand can position and orient the needle cannula in space by appropriatelypositioning and orienting the actuated platform 32 of the robot relativeto its base plate 41. Inside the robotic needle manipulator, there is aneedle driving mechanism to be described in FIGS. 5 and 6. The baseplate 41 of the robotic needle manipulator may be connected to thesemi-active arm 13 by spherical or U-joints enabling orientation of thedevice on the skin of the patient.

Reference is now made to FIG. 4 where the modified Stewart-Goughplatform is shown in close up. The base plate 41 is placed on thepatient's skin. The base may have a soft pillow 42 to conform to thebody of the patient. Although FIGS. 4 and 5 show a 6-DOF modifiedStewart-Gough robot, it is to be understood that the robotic needlemanipulator could utilize any suitable type of robotic platform, whetherparallel, such as the Stewart-Gough, or serial, or hybrid.

The robotic needle manipulator shown in FIGS. 1 to 4 may be used eitheras a simple robotic needle positioning and orientating device, such ascould be used by the physician for manual insertion of the needle, or itcould incorporate a needle driving mechanism, such that the needleinsertion too could be performed under robotic control. Reference is nowmade to FIG. 5 and FIG. 6 where an example of such a needle drivingmechanism is shown in two different insertion orientation angles,employing rotation of two or more rollers 51. The driving force iscreated by non-sliding friction between the needle shaft 31 and therollers 51. After passing the rollers the needle is traversed through adirecting cannula 53, which more precisely controls the direction of theexiting needle. Also shown schematically in FIGS. 5 and 6 is a needlerotation mechanism 54. This mechanism could be based on a pair offriction rollers aligned with their axes in the plane essentiallyparallel to the shaft of the needle, or on a single driven pulley wheelin that plane, with the needle shaft passing through a friction clutchat its center, such that application of the clutch and rotation of thepulley wheel will rotate the needle, or by any other of the knownmechanisms for providing such selectable rotation motion. Any suchrotation mechanism must allow free longitudinal motion of the needlewhen an insertion step is actuated.

Reference is now made to FIG. 7 where a spatial simulation of a priorart example of needle steering by steering of the needle base is shown.The simulation is based on the system described in PCT publishedapplication WO 2007/141784 A2. The axes, which represent thelongitudinal and lateral views of the needle environment, are marked incm. The needle holder 71 holds the base 34 of the needle 31 andmanipulates the base of the needle as shown. It can be seen that theworkspace required for the robot manipulator to insert the needle has tobe at least the height of the needle. For instance, to insert the needle6 cm into the subject's body, the workspace of the robot manipulator hasto be at least 6 cm in length and, for the orientation manipulationsshown in the simulation of FIG. 7, about 5-6 cm in width, which is theextent of lateral travel of the needle base 34. In medical applications,a robot having a large workspace is disadvantageous because of safetyissues. Large workspace means that the robot can move accidently to thewrong place.

Reference is now made to FIG. 8 where there is shown an example ofneedle steering by manipulation of its shaft using the robotic needlemanipulator of the present application. The needle is required torealize the same trajectory as in FIG. 7, but it can be seen that therobot manipulator workspace required is much smaller, because themanipulator is very close to the skin. In the example shown theworkspace is seen to be only 2 cm. high, and the width approximately 3cm. The height is dependent on the type of robot used, but typicalrobots of height even up to 5 cm. still show a workspace advantage overthe prior art methods of robotic needle insertion. Robots made for sucha small workspace have a significant advantage relating to safety sincethe manipulator is physically constrained to small area and cannot harmthe nearby areas. Furthermore, the decoupling of the position andorientation manipulation mechanisms from the pushing mechanism alsocontributes to increased safety. Additionally, the workspace of therobot is flat or planar and doesn't depend on the needle length. Thesame robot can accommodate needles of effectively any practically usedlength. Furthermore, the robot can be more easily accommodated in thelimited confines of a tomographic imaging system.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and subcombinations of various featuresdescribed hereinabove as well as variations and modifications theretowhich would occur to a person of skill in the art upon reading the abovedescription and which are not in the prior art.

1-19. (canceled)
 20. A robotic needle manipulator for steering a needlewithin soft tissue of the subject by manipulating a shaft of the needleat its distal end, comprising: a robotic platform having a plurality ofdegrees of freedom; and a needle gripper configured to be attached tothe robotic platform and to grip the needle, the needle grippercomprising a needle driving mechanism configured to provide insertionmotion to the needle in a longitudinal direction of the needle, whereincoordinated activation of the robotic platform and the needle drivingmechanism results in adjustment of the orientation angle of the needleinside the soft tissue of the subject during insertion motion of theneedle in the longitudinal direction, such that the needle traverses anon-linear path within the soft tissue of the subject.
 21. The roboticneedle manipulator of claim 20, wherein the attachment of the needlegripper to the robotic platform is such that upon coupling the needle tothe needle gripper, the needle driving mechanism is positioned at thedistal end of the needle shaft.
 22. The robotic needle manipulator ofclaim 20, wherein the needle driving mechanism comprises at least a pairof rollers on either side of the needle, such that coordinated rotationof the rollers causes the needle to move in the longitudinal direction.23. The robotic needle manipulator of claim 20, wherein the roboticplatform comprises an actuated platform and a base plate, the base platebeing configured for positioning on the subject.
 24. The robotic needlemanipulator of claim 23, further comprising a positioning systemconfigured for positioning the base plate close to a point of insertionof the needle into the body of the subject.
 25. The robotic needlemanipulator of claim 20, further comprising a needle rotation mechanismconfigured to rotate the needle about its axis.
 26. The robotic needlemanipulator of claim 20, further comprising a sensor system fordetecting motion of the body of the subject.
 27. The robotic needlemanipulator of claim 26, wherein the sensor system is configured todefine a breath cycle of the subject.
 28. A robotic needle manipulatorfor steering a needle within soft tissue of the subject by manipulatinga shaft of the needle at its distal end, comprising: a robotic platformcomprising an actuated platform having a plurality of degrees offreedom; and a needle gripper configured to be attached to the actuatedplatform and to provide insertion motion to the needle in a longitudinaldirection of the needle, wherein the actuated platform and the needlegripper are configured to be activated in coordination, such that thecoordinated activation of the actuated platform and the needle gripperenables adjustment of the orientation angle of the needle inside thesoft tissue of the subject during insertion motion of the needle withinthe soft tissue of the subject.
 29. The robotic needle manipulator ofclaim 28, wherein the robotic platform further comprises a base plateconfigured for positioning on the subject.
 30. The robotic needlemanipulator of claim 29, wherein the robotic platform is adapted toposition and orient the needle in space by appropriately positioning andorienting the actuated platform relative to the base plate to achieve adesired pose of the needle.
 31. The robotic needle manipulator of claim28, wherein the needle gripper comprises a needle driving mechanismconfigured to provide the insertion motion to the needle in alongitudinal direction.
 32. The robotic needle manipulator of claim 31,wherein the needle driving mechanism comprises at least a pair ofrollers on either side of the needle, such that coordinated rotation ofthe rollers causes the needle to move in the longitudinal direction. 33.The robotic needle manipulator of claim 31, wherein the attachment ofthe needle gripper to the actuated platform is such that upon couplingthe needle to the needle gripper, the needle driving mechanism ispositioned at the distal end of the needle shaft.
 34. The robotic needlemanipulator of claim 28, further comprising a semi-active support armconfigured to align the robotic platform close to a point of insertionof the needle into a body of the subject.
 35. The robotic needlemanipulator of claim 34, wherein the semi-active support arm isconfigured to apply pressure to the robotic platform, such that therobotic platform remains in contact with the body of the subject. 36.The robotic needle manipulator of claim 34, wherein the semi-activesupport arm is configured such that its motion is essentiallyunconstrained in a direction perpendicular to a surface of the body ofthe subject, such that the robotic platform moves freely with motion ofthe body of the subject.
 37. The robotic needle manipulator of claim 34,wherein the semi-active support arm is configured to constrain therobotic platform to a predetermined position on the body of the subject.